Refactor packetimpact Connection types

Reorganize the Connection types such that the defined types no longer expose
the lower-level functions SendFrame and CreateFrame. These methods are still
exported on the underlying Connection type, and thus can be accessed via a
type-cast. In future, defined types should have one or more type-safe versions
of the send() method on Connection, e.g. UDPIPv4 has Send() which allows the UDP
header to be overridden and SendIP() which allows both the IPv4 and UDP headers
to be modified.

testbench.Connection gets a SendFrameStateless method which sends frames
without updating the state of any of the layers. This should be used when
sending out-of-band control messages such as ICMP messages, as using the
normal Send method can result in errors when attempting to update the TCP
state using an ICMP packet.

Also remove the localAddr field of testbench.Connection and instead compute
it on the fly as needed for UDPIPv4 and TCPIPv4.

PiperOrigin-RevId: 315969714

4 files changed, 17 insertions, 19 deletions

diff --git a/test/packetimpact/tests/icmpv6_param_problem_test.go b/test/packetimpact/tests/icmpv6_param_problem_test.go
index 961059fc1..4d1d9a7f5 100644
--- a/test/packetimpact/tests/icmpv6_param_problem_test.go
+++ b/test/packetimpact/tests/icmpv6_param_problem_test.go
@@ -45,8 +45,8 @@ func TestICMPv6ParamProblemTest(t *testing.T) {
 		NDPPayload: []byte("hello world"),
 	}
 
-	toSend := conn.CreateFrame(ipv6, &icmpv6)
-	conn.SendFrame(toSend)
+	toSend := (*testbench.Connection)(&conn).CreateFrame(testbench.Layers{&ipv6}, &icmpv6)
+	(*testbench.Connection)(&conn).SendFrame(toSend)
 
 	// Build the expected ICMPv6 payload, which includes an index to the
 	// problematic byte and also the problematic packet as described in
diff --git a/test/packetimpact/tests/udp_icmp_error_propagation_test.go b/test/packetimpact/tests/udp_icmp_error_propagation_test.go
index aedabf9de..b754918f6 100644
--- a/test/packetimpact/tests/udp_icmp_error_propagation_test.go
+++ b/test/packetimpact/tests/udp_icmp_error_propagation_test.go
@@ -96,24 +96,25 @@ func wantErrno(c connectionMode, icmpErr icmpError) syscall.Errno {
 
 // sendICMPError sends an ICMP error message in response to a UDP datagram.
 func sendICMPError(conn *testbench.UDPIPv4, icmpErr icmpError, udp *testbench.UDP) error {
+	layers := (*testbench.Connection)(conn).CreateFrame(nil)
+	layers = layers[:len(layers)-1]
+	ip, ok := udp.Prev().(*testbench.IPv4)
+	if !ok {
+		return fmt.Errorf("expected %s to be IPv4", udp.Prev())
+	}
 	if icmpErr == timeToLiveExceeded {
-		ip, ok := udp.Prev().(*testbench.IPv4)
-		if !ok {
-			return fmt.Errorf("expected %s to be IPv4", udp.Prev())
-		}
 		*ip.TTL = 1
 		// Let serialization recalculate the checksum since we set the TTL
 		// to 1.
 		ip.Checksum = nil
-
-		// Note that the ICMP payload is valid in this case because the UDP
-		// payload is empty. If the UDP payload were not empty, the packet
-		// length during serialization may not be calculated correctly,
-		// resulting in a mal-formed packet.
-		conn.SendIP(icmpErr.ToICMPv4(), ip, udp)
-	} else {
-		conn.SendIP(icmpErr.ToICMPv4(), udp.Prev(), udp)
 	}
+	// Note that the ICMP payload is valid in this case because the UDP
+	// payload is empty. If the UDP payload were not empty, the packet
+	// length during serialization may not be calculated correctly,
+	// resulting in a mal-formed packet.
+	layers = append(layers, icmpErr.ToICMPv4(), ip, udp)
+
+	(*testbench.Connection)(conn).SendFrameStateless(layers)
 	return nil
 }
 
diff --git a/test/packetimpact/tests/udp_recv_multicast_test.go b/test/packetimpact/tests/udp_recv_multicast_test.go
index d51a34145..77a9bfa1d 100644
--- a/test/packetimpact/tests/udp_recv_multicast_test.go
+++ b/test/packetimpact/tests/udp_recv_multicast_test.go
@@ -35,8 +35,6 @@ func TestUDPRecvMulticast(t *testing.T) {
 	defer dut.Close(boundFD)
 	conn := testbench.NewUDPIPv4(t, testbench.UDP{DstPort: &remotePort}, testbench.UDP{SrcPort: &remotePort})
 	defer conn.Close()
-	frame := conn.CreateFrame(&testbench.UDP{}, &testbench.Payload{Bytes: []byte("hello world")})
-	frame[1].(*testbench.IPv4).DstAddr = testbench.Address(tcpip.Address(net.ParseIP("224.0.0.1").To4()))
-	conn.SendFrame(frame)
+	conn.SendIP(testbench.IPv4{DstAddr: testbench.Address(tcpip.Address(net.ParseIP("224.0.0.1").To4()))}, testbench.UDP{})
 	dut.Recv(boundFD, 100, 0)
 }
diff --git a/test/packetimpact/tests/udp_send_recv_dgram_test.go b/test/packetimpact/tests/udp_send_recv_dgram_test.go
index bf64803e2..a7db384ad 100644
--- a/test/packetimpact/tests/udp_send_recv_dgram_test.go
+++ b/test/packetimpact/tests/udp_send_recv_dgram_test.go
@@ -59,8 +59,7 @@ func TestUDPRecv(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			frame := conn.CreateFrame(&testbench.UDP{}, &testbench.Payload{Bytes: []byte(tc.payload)})
-			conn.SendFrame(frame)
+			conn.Send(testbench.UDP{}, &testbench.Payload{Bytes: []byte(tc.payload)})
 			if got, want := string(dut.Recv(boundFD, int32(len(tc.payload)), 0)), tc.payload; got != want {
 				t.Fatalf("received payload does not match sent payload got: %s, want: %s", got, want)
 			}